This invention relates to a biosensor. More specifically, it relates to a glucose biosensor having glucose oxidase immobilized thereon or a biosensor having an oxidoreductase immobilized thereon.
In a conventional biosensor having glucose oxidase immobilized on a working electrode, a counter electrode or the counter electrode and a reference electrodes, in addition to the working electrode, are arranged on the same plane of a flat base. In a glucose biosensor having the electrode arrangement as described above, two method are adapted to bring a measuring sample into contact with the working electrode.
The first method, which comprises dropping the measuring sample directly onto the working electrode, has a problem in that much labor and time are required from the sampling to the dropping. The second method involves the use of a structure formed of a spacer having a groove arranged on an electrode base and a cover having an air hole further arranged thereon to provide a sample suction opening part, a cylindrical part for sucking and housing the sample, and an air vent hole part. This method has an advantage that it does not take much labor and time since the measuring sample is directly guided onto the working electrode, but has a disadvantage of requiring a complicated process in element manufacture such as the setting of the sample suction opening part and the air vent hole part on both ends of the cylindrical part.
One object of this invention is to provide a glucose biosensor having glucose oxidase immobilized thereon.
The other object of this invention is to provide a biosensor easy to manufacture and measure, and thus suitable also as a disposable glucose biosensor.
The glucose biosensor of this invention has a structure requiring no air vent hole part.
In the glucose biosensor having glucose oxidase immobilized on an electrode, the upper and lower parts of a space part for sucking and housing a sample are formed of two upper and lower plates, the two plates are mutually stuck by an adhesive layer, the space part for sucking and housing the sample is constituted so as to be partially opened in the periphery and partially closed by the adhesive layer, and an electrode structure having at least glucose oxidase immobilized thereon is provided on the plate, whereby the manufacture and measurement are facilitated. When the upper and lower plates are tapered, a target sample can be precisely caught, and the roundness of the tip further provides an operational advantage such that the affected part is not damaged, for example, in blood sampling on a finger. This biosensor is thus suitable as a disposable glucose biosensor.
The two plates constituting the space part are stuck together only by an adhesive layer or by a spacer with adhesive on both sides. The two-plates are constituted as follows. In the first embodiment, the electrode structure is formed within the same plane on the same base, and this base is stuck to the other plate (cover) through the adhesive layer or the like. In the second embodiment, one electrode is formed on one base, and this base is stuck to the other base having one electrode or two electrodes formed thereon so as to have a facing structure in which the electrodes are mutually opposed on the inside. In both cases, the upper and lower parts of the space part for sucking and housing the sample are formed of two plates, the two plates are mutually stuck by the adhesive layer or the like, the space part for sucking and housing the sample is constituted so as to be partially opened in the peripheral part and partially closed by a thick part such as the adhesive layer, and the electrode structure having at least glucose oxidase immobilized thereon is provided on the plate.
The use of the spacer with adhesive on both sides is given herein as an example to mutually stick the upper and lower plates, but the manufacturing process can be simplified by the use of only the adhesive layer as described below. In a biosensor in which a working electrode having an oxidoreductase immobilized thereon and its counter electrode are arranged so as to have a facing structure, for example, each base having each electrode on the inside is adhered together through the adhesive layer, whereby an inexpensive manufacturing method can be realized.
The biosensor requires a connector having a special structure since lead parts for ensuring electric continuity are mutually opposed in the inner part.
Biosensors which do not require such a connector are described below.
(1 ) A biosensor which comprises a working electrode and a counter electrode formed on the inside of a longer lower base and a shorter upper base through an adhesive layer or a spacer, respectively, and a lead part for each electrode formed in such a manner that the end part is situated in a position on the lower base never superposed on the upper base, the electrode on the upper base being conducted to its lead part through an adhesive layer or a spacer.
(2 ) A biosensor which comprises a working electrode and a counter electrode formed on the inside of a longer upper base and a shorter lower base through an adhesive layer or a spacer, respectively, and a lead part for each electrode formed on the surface side of the upper base, the electrode provided on the upper base being conducted to its lead part through the base, and the electrode provided on the lower base being conducted to its lead part provided on the upper base through an adhesive layer or a spacer.
This invention also provides a biosensor device enhanced in reliability of the device, improved in a series of operability up to measurement end, and advantageous in cost by avoiding the operation by the wrong recognition in insertion of a foreign matter other than the sensor.
Such a device comprises an element reaction sensor member to be inserted to the connector part of a device body in such a manner as to be attachable and detachable, the element reaction sensor member having each output terminal of a working electrode and a counter electrode electrically connected to the connector part-side input terminals, and an element reaction part formed at least on the working electrode. The element reaction sensor member, further has a sensor insertion judging electrode, and the connector part of the device body also has two input terminals with which the sensor insertion judging electrode output terminal makes contact, so that the system of the device body is started by the contact with the two input terminals to judge the sensor insertion by a control part.